The present invention relates to a method of and an apparatus for controlling an engine to produce an engine output at a desired rotational angle of the engine such as in fuel injection control or ignition timing control.
There is known a computer-operated fuel injection control system incorporating a solenoid-operated valve for spilling a metered quantity of fuel to a diesel engine according to the control method of the type described above. The fuel injection control system is supplied with a reference signal G each time the engine crank shaft rotates through 180.degree. (crank angle=CA) and an angle signal N for each .theta.o.times.CA. If it is desired to energize the solenoid-operated valve (that is, to comlete fuel injection) after .theta. from the reference signal, then the computer determines .theta./.theta.o=k with a remainder .theta.h, then calculates h=(1/N).times.(.theta.h/360) from an average value N of rotational angle signals N, and energizes the solenoid-operated spill valve upon elapse of a time h after k rotational angle signals N have been generated. The angles of rotation of the crank shaft are counted by a finite number of signals N which are converted into a time, and an angle smaller than an interval between adjacent signals N is converted into a time based on the number of r.p.m. of the engine at the time.
The prior fuel injection control system would suffer no problem if the engine rotation were smooth and has no variations. However, the engine is actually subjected to rotational variations or irregularities in its one cycle of operation due to different engine strokes such as compression and explosion strokes. If there is any difference between the average number of r.p.m. N and the number of r.p.m. Nx at the time angle-to-time conversion is effected, then the time h will contain an error.